Just serve html and use the viewport meta tag with width=device-width. Don't serve mobile devices plain text as they'll render at whatever their default viewpor

Just serve html and use the viewport meta tag with width=device-width. Don't serve mobile devices plain text as they'll render at whatever their default viewport width is set to, 980px for Safari on iOS, which makes the text super annoying to read. Desktop browsers ignore the viewport tag and mobile browsers respect it. The page is rendered how you want everywhere for little effort.